1. Field of the Invention
This invention provides a new and improved process for making fluorozirconate glasses intended for use in numerous applications requiring excellent optical transparency from the ultraviolet to the infrared portion of the electromagnetic wavelength spectrum. This invention describes an optimum process for preparing fluoride glasses which eliminates most, if not all, of the disadvantages of prior art fluoride glasses.
2. Description of the Prior Art
Multi-component fluorozirconate glasses, a relatively new class of materials, were reported first by N. M. Chanthanasinh in his doctoral thesis for the University of Rennes (France) in July of 1976 and later by Poulain et al in the Material Research Bulletin 12, 151 (1977). Both authors were concerned with the zirconium tetrafluoride-thorium tetrafluoride-barium fluoride (ZrF.sub.4 -ThF.sub.4 -BaF.sub.2) system.
The preparation technique typically used by these earlier workers consisted of reacting highly purified components at 800.degree. to 900.degree. C. in an argon atmosphere. The starting materials used in the above system were contained in a hermetically-sealed nickel crucible and the glass produced by the system was formed by pouring the fully reacted melt into a mold residing in a nitrogen-filled glove box.
The vitreous domain for ZrF.sub.4 -ThF.sub.4 -BaF.sub.2 was described as an area of a triangle on the ternary diagram bounded by the following maxima: 63 mole percent ZrF.sub.4 ; 15 mole percent ThF.sub.4 ; and 38 mole percent BaF.sub.2. Fluoride glasses prepared in accordance with these teachings are unacceptable for our intended uses, because of their absorption and physical strength characteristics.
Applicants know of no other prior art that is as relevant as that identified and described above.